Battery cell, negative active material, method for producing the same, and battery device

Abstract

The application discloses a battery monomer, a negative electrode active material and a preparation method thereof, and a battery device. The battery monomer comprises a negative electrode sheet and a positive electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector and comprising a negative electrode active material; the negative electrode active material comprises a graphite inner core and a coating layer at least partially covering the surface of the graphite inner core; the coating layer comprises one or more of carbon elements and metal elements; wherein the carbon elements comprise amorphous carbon, and the metal elements are grafted on the surface of the graphite inner core and / or in the coating layer through chemical bonds. According to the embodiment of the application, the interface impedance of the negative electrode active material can be reduced, the charge transfer impedance of the battery monomer can be reduced, and the charging capacity of the battery monomer can be improved.

Description

Technical Field

[0001] This application relates to battery cells, and more particularly to a battery cell, a negative electrode active material and its preparation method, and a battery device. Background Technology

[0002] Because battery cells can convert chemical energy into electrical energy, they have become one of the important energy sources for human production and life, and are therefore widely used in many fields such as power tools, electric vehicles, and electronic devices to provide them with power.

[0003] With the widespread application of battery cells in various fields, the requirements for their performance are becoming increasingly stringent. Among these requirements, the negative electrode active material of battery cells has become a key focus. Therefore, improving the performance of negative electrode active materials is one of the urgent technical problems that needs to be solved in battery cell development. Summary of the Invention

[0004] This application provides a battery cell, a negative electrode active material, a method for preparing the same, and a battery device, which can reduce the interfacial impedance of the negative electrode active material, reduce the charge transfer impedance of the battery cell, and improve the charging capability of the battery cell.

[0005] In a first aspect, embodiments of this application provide a battery cell, including a negative electrode sheet and a positive electrode sheet. The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and including a negative electrode active material. The negative electrode active material includes a graphite core and a coating layer at least partially covering the surface of the graphite core. The coating layer includes one or more of carbon elements and metal elements. The carbon elements include amorphous carbon, and the metal elements are grafted onto the surface of the graphite core and / or the coating layer through chemical bonds.

[0006] This application embodiment increases the number of lithium active sites on the graphite surface by coating the graphite core with a coating layer containing metal elements, thereby improving lithium-ion transport. Simultaneously, the metal elements are fixed by chemical bonds, reducing the possibility of metal precipitation. This further reduces the interfacial impedance of the graphite material, resulting in lower charge transfer impedance and improved charging capability when used in battery cells.

[0007] In any embodiment of this application, metal elements are grafted onto the surface of the graphite core and / or the coating layer via carbon-oxygen bonds.

[0008] In any embodiment of this application, the metal element is grafted onto the surface of the graphite core and / or the coating layer in the form of -COM group and / or -CM group; wherein, M is a metal element, and M includes one or more of lithium, magnesium, aluminum, titanium, calcium, zinc and tin.

[0009] In any embodiment of this application, the mass content of the metal element based on the negative electrode active material is 0.1% to 10%.

[0010] In any embodiment of this application, the graphite content is 90% to 99.9% based on the negative electrode active material.

[0011] In any embodiment of this application, graphite includes one or more of artificial graphite, natural graphite, mesophase carbon microspheres, and hard carbon.

[0012] In any embodiment of this application, the average volumetric particle size Dv50 of graphite is 1–30 μm.

[0013] In any embodiment of this application, the average volumetric particle size Dv50 of graphite is 5–10 μm.

[0014] In any embodiment of this application, the thickness of the coating layer is 1–20 nm.

[0015] In any embodiment of this application, the compaction density of the coating layer is 1.6 g / cm³. 3 ~1.9g / cm 3 .

[0016] In any embodiment of this application, the coating layer covers at least 80% of the surface area of ​​the graphite core.

[0017] In any embodiment of this application, the resistivity of the negative electrode active material is 1*10⁻⁶. -6 Ωm~3*10 -6 Ωm.

[0018] Secondly, embodiments of this application provide a negative electrode active material, which includes a graphite core and a coating layer at least partially covering the surface of the graphite core; the coating layer includes one or more of carbon elements and metal elements; wherein the carbon elements include amorphous carbon, and the metal elements are grafted onto the surface of the graphite core and / or the coating layer through chemical bonds.

[0019] This application embodiment increases the number of lithium active sites on the graphite surface by coating the graphite core with a coating layer containing metal elements, thereby improving lithium-ion transport. Simultaneously, the metal elements are fixed by chemical bonds, reducing the possibility of metal precipitation. This further reduces the interfacial impedance of the graphite material, resulting in lower charge transfer impedance and improved charging capability when used in battery cells.

[0020] Thirdly, embodiments of this application provide a method for preparing a negative electrode active material, comprising: mixing a carbon source containing metal elements and graphite to obtain a precursor; subjecting the precursor to heat treatment to obtain a negative electrode active material; the negative electrode active material comprising a graphite core and a coating layer at least partially covering the surface of the graphite core; the coating layer comprising one or more of carbon elements and metal elements; wherein the carbon elements comprise amorphous carbon, and the metal elements are grafted onto the surface of the graphite core and / or the coating layer through chemical bonds.

[0021] This application embodiment decomposes a carbon source containing metal elements at high temperature, thereby fixing the metal elements through chemical bonds while forming a graphite coating layer, reducing the possibility of metal element precipitation. This better reduces the interfacial impedance of the graphite material, and when used in battery cells, it reduces the charge transfer impedance of the battery cell and improves the charging capability of the battery cell.

[0022] In any embodiment of this application, the carbon source includes an organometallic salt, which includes one or more of metal alkoxides and metal phenolates.

[0023] In any embodiment of this application, the metal alkoxide includes one or more of metal isopropoxide, metal ethanol, and metal methanol, and the metal phenolic salt includes one or more of metal phenolic salt and metal nitrophenolic salt. The metal element includes one or more of lithium, magnesium, aluminum, titanium, calcium, zinc, and tin.

[0024] In any embodiment of this application, graphite includes one or more of artificial graphite, natural graphite, mesophase carbon microspheres, and hard carbon.

[0025] In any embodiment of this application, the mass content of the carbon source based on the precursor is 1% to 30%.

[0026] In any embodiment of this application, the mass content of the carbon source based on the precursor is 5% to 20%.

[0027] In any embodiment of this application, the mixing process includes one or more of the following: sol-gel method, ball milling method, and stirring method.

[0028] In any embodiment of this application, the heat treatment temperature is 500–1200°C and the time is 4–8 hours.

[0029] In any embodiment of this application, the heat treatment temperature is 600–1000°C and the time is 4–8 hours.

[0030] In any embodiment of this application, the heat treatment pressure is 5 to 15 MPa.

[0031] Fourthly, embodiments of this application provide a battery device including a battery cell from the first aspect. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 The diagram shows a schematic of a battery cell provided in some embodiments of this application.

[0034] Figure 2 A schematic diagram of an electrical device provided in some embodiments of this application is shown.

[0035] Figure 3 The diagram shows a schematic representation of the structure of the negative electrode active material provided in some embodiments of this application.

[0036] Figure 4 SEM images of the negative electrode active materials provided in Example 1 and Comparative Example 1 of this application are shown, where the scale bar is 1 μm.

[0037] Figure 5 The XRD patterns of the negative electrode active materials provided in Example 1 and Comparative Example 1 of this application are shown.

[0038] Figure 6 The rate performance diagrams of the button cells provided in Embodiment 1 and Comparative Examples 1-2 of this application are shown.

[0039] Figure 7 The AC impedance diagrams of the stacked three-electrode provided in Embodiment 1 and Comparative Example 1 of this application are shown.

[0040] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0041] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0042] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0043] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, negative electrode active material, preparation method thereof, and battery device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0044] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0046] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0047] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0048] Unless otherwise specified, in this application, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0049] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0050] In the description of the embodiments of this application, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0051] Unless otherwise stated, the test temperature for all parameters mentioned in this application is 25°C.

[0052] The battery cells mentioned in the embodiments of this application are capable of charging and discharging independently. The battery cells may be cylindrical, cuboid, or other shapes, and the embodiments of this application are not limited in this respect. Figure 1 This is a cuboid-shaped battery cell used as an example.

[0053] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0054] The battery cell provided in the embodiments of this application includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator disposed between the negative electrode and the positive electrode. During the charging and discharging process of the battery cell, active ions (e.g., lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, disposed between the positive and negative electrodes, serves to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through. The electrode assembly can be a wound structure or a stacked structure; the embodiments of this application are not limited in this regard.

[0055] The battery cell also includes an outer packaging, which encapsulates the electrode components and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. It can also be a flexible package, such as a pouch. The material of the flexible package can be plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0056] The battery cells provided in the embodiments of this application can be lithium-ion battery cells, sodium-ion battery cells, sodium-lithium-ion battery cells, lithium metal battery cells, sodium metal battery cells, lithium-sulfur battery cells, magnesium-ion battery cells, nickel-metal hydride battery cells, nickel-cadmium battery cells, lead-acid battery cells, etc., and the embodiments of this application are not limited to these.

[0057] The method for preparing the battery cell of this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained.

[0058] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0059] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0060] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0061] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0062] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0063] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0064] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0065] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0066] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0067] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. Battery cells and battery devices are used to store or provide electrical energy.

[0068] Figure 2 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0069] The negative electrode active material in related technologies is usually conventional graphite material, and the surface coating of conventional graphite material is mostly amorphous carbon.

[0070] However, amorphous carbon-coated graphite materials have fewer active lithium sites on their surface, and their electrochemical activity is even lower at low temperatures, further reducing lithium-ion transport capacity. This leads to increased interfacial impedance of the graphite material at low temperatures, a sharp increase in charge transfer impedance of the battery cell, and a significant reduction in the charging capacity of the battery cell at low temperatures.

[0071] Therefore, embodiments of this application provide a battery cell, a negative electrode active material, a method for preparing the same, and a battery device, which can reduce the interfacial impedance of the negative electrode active material, reduce the charge transfer impedance of the battery cell, and improve the charging capability of the battery cell.

[0072] battery cell

[0073] This application provides a battery cell including a negative electrode and a positive electrode. The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and including a negative electrode active material. The negative electrode active material includes a graphite core and a coating layer at least partially covering the surface of the graphite core. The coating layer includes one or more of carbon elements and metal elements. The carbon elements include amorphous carbon, and the metal elements are grafted onto the surface of the graphite core and / or the coating layer through chemical bonds.

[0074] Related technologies use silane coupling agents and active particles to modify nano-metal powders to prepare metal-coated graphite materials. These modified graphite materials contain silicon oxides, which react with lithium ions to form irreversible lithium silicides, thus consuming active lithium and reducing the initial coulombic efficiency. Furthermore, the high heat treatment temperature during production easily leads to resource waste.

[0075] This application embodiment coats the graphite core surface with a coating layer containing metal elements. Metal elements have low nucleation sites and excellent lithium affinity, which increases the number of lithium active sites on the graphite surface, thereby improving lithium-ion transport capacity. Furthermore, the negative electrode active material in this application embodiment does not contain silicon oxide compounds, thus avoiding the consumption of active lithium and improving the initial coulombic efficiency.

[0076] Meanwhile, compared to related technologies that directly introduce metal elements as metal oxides or elemental metals into the negative electrode active material, the embodiments of this application fix the metal elements on the surface of the graphite core and / or in the coating layer through chemical bonds. The chemical bonds are stronger and typically require higher energy to break, thus reducing the possibility of metal element precipitation during charging and discharging. This better reduces the interfacial impedance of the graphite material. When used in battery cells, metal elements can be introduced into the interfacial film (such as SEI and CEI films), and charge transfer can occur through metal (π-d) charge transfer mechanisms and / or metal-metal (dd) charge transfer mechanisms, thereby reducing the charge transfer impedance of the battery cell and improving its charging capability.

[0077] The metal elements and chemical bonds in the embodiments of this application can be determined using methods known in the art, such as nuclear magnetic resonance spectroscopy.

[0078] Nuclear magnetic resonance spectroscopy is used to study the absorption of radio frequency radiation by atomic nuclei in a strong magnetic field. It is one of the most powerful tools for qualitative analysis of the composition and structure of various organic and inorganic substances, and sometimes quantitative analysis can also be performed. It can also be combined with XPS and TEM for analysis.

[0079] The following test steps can be used to detect organic functional groups using infrared spectroscopy: An infrared beam passes through a depth of a few μm on the surface of an electrode (ATR is a Ge crystal). When irradiated with infrared light of continuously varying frequencies, molecules on the electrode surface absorb radiation at certain frequencies. This absorption causes a net change in the dipole moment due to their vibrational or rotational motion, resulting in transitions from the ground state to excited states in molecular vibrational and rotational energy levels. This weakens the intensity of transmitted light corresponding to these absorption regions. Recording the percentage transmittance versus wavenumber curve yields the infrared spectrum. The infrared spectrum and functional group analysis results are then obtained. For example, the national standard GB / T6040-2002, "General Rules for Infrared Spectroscopic Analysis," can be referenced. Alternatively, ICP testing can be used, for example, referring to standards YS / T1006.2-2014, GB / T23367.2-2009, or YS / T1028.5-2015.

[0080] Alternatively, an ICP inductively coupled plasma atomic emission spectrometer (model iCAP 740) can be used, and measurements can be performed according to the manufacturer's instructions. Further analysis can be performed by combining pyrolysis gravimetric analysis and gas chromatography-mass spectrometry.

[0081] In some embodiments, in order to better reduce the interfacial impedance of graphite materials, metal elements are grafted onto the surface of the graphite core and / or the coating layer via carbon-oxygen bonds.

[0082] In some embodiments, to better reduce the interfacial impedance of graphite materials, metal elements are grafted onto the graphite core surface and / or coating layer in the form of -COM groups and / or -CM groups; wherein, M is a metal element, and M includes one or more of lithium, magnesium, aluminum, titanium, calcium, zinc, and tin. Those skilled in the art can adjust the positions of different groups as needed. For example, metal elements can be grafted onto the graphite core surface in the form of -COM groups; metal elements can be grafted into the coating layer in the form of -COM groups; metal elements can be grafted onto both the graphite core surface and the coating layer in the form of -COM groups; metal elements can be grafted onto the graphite core surface in the form of -CM groups; metal elements can be grafted into the coating layer in the form of -CM groups; metal elements can be grafted onto both the graphite core surface and the coating layer in the form of -CM groups.

[0083] In some embodiments, in order to improve the specific capacity of the negative electrode active material while better reducing the interfacial impedance of the negative electrode active material, reducing the charge transfer impedance of the battery cell, and improving the charging capacity of the battery cell, the mass content of the metal element based on the negative electrode active material is 0.1% to 10%.

[0084] When the mass content of metal elements is within a suitable range, based on the total mass of the negative electrode film, the mass content of graphite material can also be within a suitable range, thereby increasing the specific capacity of graphite material.

[0085] Optionally, based on the negative electrode active material, the mass content of the metal element is independently selected from 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, and 2.2%. 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7 The value is any one of 7%, 7.8%, 7.9%, 8.0%, 8.1%, 8.2%, 8.3%, 8.4%, 8.5%, 8.6%, 8.7%, 8.8%, 8.9%, 9.0%, 9.1%, 9.2%, 9.3%, 9.4%, 9.5%, 9.6%, 9.7%, 9.8%, 9.9%, or 10.0%, or a range between any two.

[0086] In this embodiment, the mass content of the metal element can be determined using methods known in the art. For example, 0.2 g of sample is weighed into a 100 mL beaker, 10 mL of 10% nitric acid solution is added, and the mixture is heated at 120 °C for 0.5 h to digest the sample. The solution is then diluted to volume with a 100 mL volumetric flask. 1 mL of the diluted solution is then transferred to the 100 mL volumetric flask and diluted to volume to obtain the test solution. The element content in the test solution is determined using an inductively coupled plasma optical emission spectrometer (ICP-OES, Agilent 5800).

[0087] In some embodiments, in order to improve the specific capacity of the negative electrode active material while better reducing the interfacial impedance of the negative electrode active material, reducing the charge transfer impedance of the battery cell, and improving the charging capacity of the battery cell, the graphite content of the negative electrode active material is 90% to 99.9% by mass.

[0088] The specific capacity of the negative electrode active material in this application embodiment is mainly provided by the carbon element in the core. The graphite core mass content within this appropriate range can balance the specific capacity of the graphite material and the contribution of the metal elements in the coating layer to reducing the interface impedance.

[0089] In the embodiments of this application, the mass content of graphite can be determined using methods known in the art, such as: using a thermal analysis weight loss analyzer of model TGA 8000, and according to the general rules of thermal analysis method JYT014-1996, the temperature is raised to 800°C under an air atmosphere to conduct the experiment, and the graphite content can be determined based on the experimental data.

[0090] Optionally, based on the negative electrode active material, the mass content of graphite is independently selected from 90.0%, 90.2%, 90.4%, 90.6%, 90.8%, 91.0%, 91.2%, 91.4%, 91.6%, 91.8%, 92.0%, 92.2%, 92.4%, 92.6%, 92.8%, 93.0%, 93.2%, 93.4%, 93.6%, 93.8%, 94.0%, 94.2%, 94.4%, 94.6%, 94.8%, 95.0%, and 95.2%. The value is any value from %, 95.4%, 95.6%, 95.8%, 96.0%, 96.2%, 96.4%, 96.6%, 96.8%, 97.0%, 97.2%, 97.4%, 97.6%, 97.8%, 98.0%, 98.2%, 98.4%, 98.6%, 98.8%, 99.0%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or a range between any two.

[0091] In some embodiments, graphite includes one or more of artificial graphite, natural graphite, mesophase carbon microspheres, and hard carbon.

[0092] Artificial graphite is made from natural graphite through dozens of processes, including high-temperature baking and chemical treatment. It possesses excellent electrical conductivity, high strength and toughness, and good electrochemical stability. These properties make it a preferred material for manufacturing the negative electrode of battery cells, effectively preventing side reactions between lithium ions and the negative electrode active material during charging and discharging, thus extending the lifespan of lithium batteries.

[0093] Natural graphite is generally made from natural flake graphite, which is modified to form spherical natural graphite for use. Although natural graphite has problems such as numerous surface defects and poor electrolyte tolerance, its performance can be significantly improved through modification treatments, such as surface etching, oxidation, fluorination, or coating modification. In battery cells, natural graphite can efficiently insert and release lithium ions, making it an ideal negative electrode active material.

[0094] Mesophase carbon microspheres are a novel carbon material with high surface area, excellent conductivity, and good structural stability. Their unique mesophase structure can improve the electrochemical reaction rate and energy storage capacity, thereby enhancing the rate performance of individual battery cells. Mesophase carbon microspheres can be combined with various anode active materials to form composite materials, improving the conductivity and lithium storage capacity of the anode active materials.

[0095] Hard carbon is carbon that does not graphitize after high-temperature treatment. Its internal crystal arrangement is disordered with large interlayer spacing, allowing the hard carbon anode to store more charge in the same volume, thus improving the energy density and range of the battery cell. Furthermore, hard carbon has a stable structure, long charge-discharge cycle life, and better safety performance. However, hard carbon also has drawbacks, such as lower initial charge-discharge efficiency compared to graphitized carbon.

[0096] In the embodiments of this application, the composition and ratio of carbon materials in the graphite core can be adjusted as needed. For example, they can be adjusted according to the characteristics of different carbon materials so that the performance of the graphite core meets the expected requirements.

[0097] In some embodiments, the average volumetric particle size Dv50 of graphite is 1–30 μm.

[0098] Optionally, the average volumetric particle size Dv50 of graphite is 5–10 μm.

[0099] In the embodiments of this application, graphite with a suitable range of volumetric particle size can reduce the weight of the required coating layer, thereby increasing the mass ratio of the graphite core in the negative electrode active material, and thus increasing the specific capacity of the negative electrode active material.

[0100] Optionally, the average volumetric particle size Dv50 of graphite is independently selected from any value or a range between 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, and 30 μm.

[0101] Dv50 represents the particle size corresponding to a cumulative volumetric distribution percentage of 50% for the material. It can be measured using a laser particle size analyzer, referring to GB / T19077-2016. During testing, add 1g of the sample to a clean small beaker, along with 20ml of deionized water. Sonicate at 53kHz / 120W for 5 minutes to ensure complete dispersion. Turn on the laser particle size analyzer, clean the optical path system, and automatically test the background. Stir the sonicated solution to ensure uniform dispersion, then place it in the sample cell as required and begin measuring the particle size. A MasterSizer 3000 laser particle size analyzer can be used as the testing instrument.

[0102] In some embodiments, the thickness of the coating layer is 1–20 nm.

[0103] The coating layer in this embodiment provides additional protection for the negative electrode active material, reducing mechanical stress caused by volume expansion and contraction during charging and discharging, thereby delaying the aging and performance degradation of the negative electrode active material. Simultaneously, it reduces the possibility of the coating layer limiting the lithium-ion diffusion rate and the likelihood of the coating layer increasing the weight and volume of the negative electrode active material, thus improving the structural stability, conductivity, and specific capacity of the negative electrode active material. Therefore, the coating layer with a suitable thickness in this embodiment, used in battery cells, can improve the cycle life and capacity retention of the battery cells.

[0104] Optionally, the thickness of the coating layer is independently selected from any value or a range between 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, and 20nm.

[0105] The thickness of the coating layer can be determined using methods known in the art. As an example, a cross-section of the negative electrode active material particles can be prepared using a cross-section polisher (such as the JEOL IB-09010CP argon ion cross-section polisher), passing through the core of the particles. Then, elemental analysis using EDX or EDS combined with TEM or SEM (such as the Oxford Instruments X-Max EDS combined with the ZEISS Sigma-02-33 SEM) is performed to obtain an elemental distribution map of the cross-section. The thickness of the coating layer is then determined based on the elemental distribution of the cross-section. More precisely, the thickness of the coating layer can be measured at multiple (more than 3, such as 8, 10, 12, etc.) different locations on the cross-section, and the average value is recorded as the coating layer thickness.

[0106] In some embodiments, the compaction density of the coating layer is 1.6 g / cm³.3 ~1.9g / cm 3 .

[0107] In this embodiment, a suitable compaction density means a high coating density. A high-density coating effectively reduces the possibility of direct contact between the graphite core and the electrolyte, thus reducing side reactions and improving the cycle stability of the battery cell. Furthermore, a dense coating reduces the likelihood of polarization during charging and discharging, ensuring consistent electron and lithium-ion transport speeds and reducing the internal resistance of the negative electrode active material. The dense coating also reduces the likelihood of cracks or peeling of the negative electrode active material during charging and discharging, decreasing the possibility of internal short circuits and improving battery cell reliability. Moreover, a dense coating facilitates rapid lithium-ion diffusion and transport, thereby improving the rate performance of the battery cell.

[0108] Optionally, the compaction density of the coating layer is independently selected from 1.60 g / cm³. 3 1.65g / cm 3 1.70g / cm 3 1.75g / cm 3 1.80g / cm 3 1.85g / cm 3 1.90g / cm 3 Any value in the range or any value between the two.

[0109] The compaction density of the coating layer can be determined using methods known in the art. As an example, it can be determined using an electronic pressure testing machine, such as the UTM7305 type, in accordance with GB / T 24533-2009 Method for Determination of Powder Compaction Density.

[0110] In some embodiments, the coating layer covers at least 80% of the surface area of ​​the graphite core.

[0111] Compared to island-like or dot-like coatings in related technologies, the coating layer in this embodiment covers at least 80% of the graphite core surface area, meaning the coating layer is uniformly applied to the graphite core surface. This reduces local current density differences and improves the interfacial impedance of the negative electrode active material. When used in a battery cell, this reduces the charge transfer impedance and improves the charging capability of the battery cell.

[0112] In some embodiments, the resistivity of the negative electrode active material is 1*10⁻⁶. -6 Ωm~3*10 -6 Ωm.

[0113] The resistivity of the negative electrode active material can be measured using methods known in the art. As an example, the resistivity of graphite material was tested using a UNI-T TU620C resistivity meter according to GB / T 6146-2010.

[0114] Optionally, the resistivity of the negative electrode active material is independently selected from 1.0*10⁻⁶. -6 Ωm, 1.1*10 -6 Ωm, 1.2*10 -6 Ωm, 1.3*10 -6 Ωm, 1.4*10 -6 Ωm, 1.5*10 -6 Ωm, 1.6*10 -6 Ωm, 1.7*10 -6 Ωm, 1.8*10 -6 Ωm, 1.9*10 -6 Ωm, 2.0*10 -6 Ωm, 2.1*10 -6 Ωm, 2.2*10 -6 Ωm, 2.3*10 -6 Ωm, 2.4*10 -6 Ωm, 2.5*10 -6 Ωm, 2.6*10 -6 Ωm, 2.7*10 -6 Ωm, 2.8*10 -6 Ωm, 2.9*10 -6 Ωm, 3.0*10 -6 Any value in Ωm or any range of values ​​between the two.

[0115] [Positive electrode plate]

[0116] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and comprising a positive electrode active material. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0117] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting lithium.

[0118] As examples, positive electrode active materials may include, but are not limited to, one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, lithium titanium oxides, and their respective modified compounds. Lithium transition metal oxides may include, but are not limited to, layered structures and spinel structures. Examples of lithium-containing phosphates may include, but are not limited to, lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, lithium iron manganese phosphate and carbon composites, and their respective modified compounds.

[0119] In some embodiments, to further improve the energy density of a single battery cell, the positive electrode active material may include materials of the general formula Li. a Ni b Co c M d O e D f One or more of lithium transition metal oxides and their modified compounds. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include, but is not limited to, one or more of Ge, Mo, Sn, Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D may include, but is not limited to, one or more of N, F, S and Cl.

[0120] In some embodiments, the positive electrode active material may simultaneously comprise lithium transition metal oxide and lithium phosphate. This is advantageous for obtaining battery cells that balance high capacity and high reliability.

[0121] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, and LiNi 1 / 2 Mn 1 / 2O2, LiMn2O4, Li 4 / 3 Ti 5 / 3 O4, LiNi 1 / 2 Mn 1 / 2 O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, Li 1.13 Ti 0.57 Fe 0.3 One or more of S2.

[0122] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting sodium. For example, the positive electrode active material may include, but is not limited to, one or more of layered transition metal oxides (including but not limited to P2 type, O3 type, etc.), polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian materials.

[0123] In some embodiments, as an example, the positive electrode active material may include, but is not limited to, NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, Na 0.67 MO2 (M includes at least two of Fe, Co, Cr, Mn, Ni, V, Ti, and Mo), NaMO2 (M includes at least two of Fe, Co, Ni, V, Ti, and Mo), NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and one or more of their respective modified compounds.

[0124] The modified compounds for the above-mentioned positive electrode active materials can be obtained by doping and / or surface coating of the positive electrode active materials.

[0125] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0126] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylate resins, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0127] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0128] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active materials, positive electrode conductive agents, positive electrode binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0129] [Negative electrode plate]

[0130] In some embodiments, the negative electrode sheet may include a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0131] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0132] In some embodiments, the negative electrode film layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0133] In some embodiments, the negative electrode film layer may also include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0134] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include, but is not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0135] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, negative electrode conductive agent, negative electrode binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0136] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet also includes a conductive undercoat layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector.

[0137] In some embodiments, the negative electrode sheet can be made of foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, foamed carbon, etc. When foamed metal is used as the negative electrode sheet, the surface of the foamed metal may or may not contain a negative electrode active material.

[0138] [Electrolytes]

[0139] This application does not impose specific limitations on the type of electrolyte, which can be selected according to requirements. For example, the electrolyte can be selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0140] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0141] Taking a lithium battery cell as an example, the electrolyte salt may include, but is not limited to, one or more of the following: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0142] Taking sodium battery cells as an example, the electrolyte salt may include, but is not limited to, one or more of the following: sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium difluorosulfonyl imide (NaFSI), sodium difluoromethanesulfonyl imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalate borate (NaDFOB), sodium dioxalate borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorodioxalate phosphate (NaDFOP), and sodium tetrafluorooxalate phosphate (NaTFOP).

[0143] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0144] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve the overcharge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature power performance of the battery cell.

[0145] [Isolation membrane]

[0146] Battery cells using electrolytes, as well as some battery cells using solid electrolytes, also include a separator. The separator is disposed between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes, while allowing metal ions to pass through. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0147] In some embodiments, the isolation membrane includes a porous base membrane and a coating located on at least one side of the porous base membrane.

[0148] In some embodiments, the material of the separator may include at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0149] In some embodiments, the coating includes a heat-resistant layer and an adhesive layer, the heat-resistant layer being disposed between the base film and the adhesive layer, the heat-resistant layer including heat-resistant particles, and the adhesive layer including organic particles.

[0150] In some embodiments, the heat-resistant particles include one or more of inorganic particles or organic particles.

[0151] In some embodiments, inorganic particles may include one or more of the following: inorganic particles having a dielectric constant of 5 or greater, inorganic particles having ion conductivity but not storing ions, or inorganic particles capable of undergoing electrochemical reactions.

[0152] In some embodiments, inorganic particles having a dielectric constant of 5 or higher may include boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxides, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, aluminum hydroxide, barium oxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, calcium fluoride, barium fluoride, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hydropyrite, Pb(Zr,Ti)O3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0 < m < 1, 0 < n < 1), Pb (Mg3Nb) 2 / 3 The inorganic particles can be selected from one or more of PbTiO3 (PMN-PT) and their respective modified inorganic particles. Optionally, the modification of each inorganic particle can be chemical modification and / or physical modification.

[0153] In some embodiments, inorganic particles that are ion-conductive but do not store ions may include Li3PO4, lithium titanium phosphate (Li3PO4), etc. x1 Ti y1 (PO4)3, Lithium aluminum titanium phosphate (Li) x2 Al y2 Ti z1 (PO4)3、(LiAlTiP) x3 O y3 Type glass, lithium lanthanum titanate (Li) x4 La y4 TiO3, lithium germanium thiophosphate Li x5 Ge y5 P z2 S w Lithium nitride (Li) x6 N y6 SiS2 type glass Li x7 Si y7 S z3 and P2S5 type glass Li x8 P y8 S z4 One or more of the following are given: 0 < x1 < 2, 0 < y1 < 3, 0 < x2 < 2, 0 < y2 < 1, 0 < z1 < 3, 0 < x3 < 4, 0 < y3 < 13, 0 < x4 < 2, 0 < y4 < 3, 0 < x5 < 4, 0 < y5 < 1, 0 < z2 < 1, 0 < w < 5, 0 < x6 < 4, 0 < y6 < 2, 0 < x7 < 3, 0 < y7 < 2, 0 < z3 < 4, 0 < x8 < 3, 0 < y8 < 3, 0 < z4 < 7. This can improve the ion conductivity of the separator.

[0154] In some embodiments, the inorganic particles capable of undergoing electrochemical reactions may include one or more of lithium-containing transition metal oxides, lithium-containing phosphates, carbon-based materials, silicon-based materials, tin-based materials, and lithium-titanium compounds.

[0155] In some embodiments, the organic particles may include at least one of a thermoplastic resin polymer, a thermosetting resin polymer, or a crosslinked polymer.

[0156] In some embodiments, the thermoplastic resin polymer may include one or more of the following: polycarbonate organic particles, polymethyl methacrylate organic particles, polyoxymethylene organic particles, polyamide organic particles, styrene-acrylonitrile copolymer, polyphenylene sulfide organic particles, polyether ether ketone organic particles, polyimide organic particles, polysulfone organic particles, polyether sulfone organic particles, polyphenylene sulfone organic particles, polybenzimidazole organic particles, polyamide-imide organic particles, and polyethyleneimine organic particles.

[0157] In some embodiments, the thermosetting resin polymer may include one or more of the following: phenolic resin organic particles, polymer particles containing triazine ring structural units, epoxy resin organic particles, unsaturated polyester resin organic particles, urea-formaldehyde resin organic particles, and furan resin organic particles.

[0158] In some embodiments, the crosslinking polymer may include one or more of crosslinked styrene organic particles and silicon-containing organic crosslinked resin particles.

[0159] In some embodiments, the coating includes an adhesive, which may include, but is not limited to, one or more of polyacrylate adhesives, nitrile rubber adhesives, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0160] In some embodiments, the coating may further include a dispersant, such as one or more of alkylphenol polyoxyethylene ethers, polyacrylic acid dispersants, and cellulose dispersants, including but not limited to. For example, the dispersant may include one or more of sodium carboxymethyl cellulose, sodium polyacrylate, and ammonium polyacrylate.

[0161] Negative electrode active materials

[0162] This application provides a negative electrode active material, which includes a graphite core and a coating layer at least partially covering the surface of the graphite core; the coating layer includes one or more of carbon elements and metal elements; wherein the carbon elements include amorphous carbon, and the metal elements are grafted onto the surface of the graphite core and / or the coating layer through chemical bonds.

[0163] This application embodiment coats the graphite core surface with a coating layer containing metal elements. Metal elements have low nucleation sites and excellent lithium affinity, which increases the number of lithium active sites on the graphite surface, thereby improving lithium-ion transport capacity. Furthermore, the negative electrode active material in this application embodiment does not contain silicon oxide compounds, thus avoiding the consumption of active lithium and improving the initial coulombic efficiency.

[0164] Meanwhile, compared to related technologies that directly introduce metal elements as metal oxides or elemental metals into the negative electrode active material, the embodiments of this application fix the metal elements on the surface of the graphite core and / or in the coating layer through chemical bonds. The chemical bonds are stronger and typically require higher energy to break, thus reducing the possibility of metal element precipitation during charging and discharging. This better reduces the interfacial impedance of the graphite material. When used in battery cells, metal elements can be introduced into the interfacial film (such as SEI and CEI films), and charge transfer can occur through metal (π-d) charge transfer mechanisms and / or metal-metal (dd) charge transfer mechanisms, thereby reducing the charge transfer impedance of the battery cell and improving its charging capability.

[0165] Preparation method of negative electrode active material

[0166] This application provides a method for preparing a negative electrode active material, comprising: mixing a carbon source containing metal elements and graphite to obtain a precursor; subjecting the precursor to heat treatment to obtain a negative electrode active material; the negative electrode active material includes a graphite core and a coating layer at least partially covering the surface of the graphite core; the coating layer includes one or more of carbon elements and metal elements; wherein the carbon elements include amorphous carbon, and the metal elements are grafted onto the surface of the graphite core and / or the coating layer through chemical bonds.

[0167] This application embodiment decomposes a carbon source containing metal elements at high temperature to first obtain carbon-containing compounds, metal oxides, and / or elemental metals. The carbon-containing compounds are further carbonized to form an amorphous carbon coating layer. Simultaneously, the metal oxides and / or elemental metals form metal-containing groups through chemical bonds, thereby fixing the metal elements on the surface of the graphite core and / or in the coating layer, reducing the possibility of metal precipitation. This better reduces the interfacial impedance of the graphite material, and when used in battery cells, it reduces the charge transfer impedance of the battery cells and improves the charging capability of the battery cells.

[0168] In some embodiments, the carbon source includes an organometallic salt, which includes one or more of metal alkoxides and metal phenolates.

[0169] Optionally, the metal alkoxide includes one or more of metal isopropoxide, metal ethanol, and metal methanol, and the metal phenolic salt includes one or more of metal phenolic salt and metal nitrophenolic salt, wherein the metal element includes one or more of lithium, magnesium, aluminum, titanium, calcium, zinc, and tin.

[0170] The metal isopropoxide has the structure shown in Formula 1, where M is a metal element:

[0171]

[0172] The composition and ratio of the carbon source in the embodiments of this application can be adjusted as needed. For example, the preset content of metal elements in the coating layer can be obtained based on the molar ratio of metal elements in different carbon sources.

[0173] In some embodiments, the purity of the carbon source can be adjusted to 80.00% to 99.99% to reduce the impact of impurities in the carbon source on the negative electrode active material.

[0174] In some embodiments, graphite includes one or more of artificial graphite, natural graphite, mesophase carbon microspheres, and hard carbon.

[0175] In some embodiments, the carbon source has a mass content of 1% to 30% based on the precursor.

[0176] Optionally, based on the precursor, the carbon source has a mass content of 5% to 20%.

[0177] Optionally, based on the precursor, the mass content of the carbon source is independently selected from any value or a range between any two of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%.

[0178] In the embodiments of this application, a coating layer with a preset thickness, uniformity, and density can be obtained by adjusting the mass content of the carbon source.

[0179] In some embodiments, the mixing process includes one or more of the following: sol-gel method, ball milling method, and stirring method.

[0180] The sol-gel method is an important material preparation method. It utilizes compounds containing highly chemically active components as precursors, uniformly mixing these raw materials in the liquid phase, and forming a stable, transparent sol system in solution through chemical reactions such as hydrolysis and condensation. After aging, the sol particles slowly polymerize to form a gel with a three-dimensional network structure, the spaces between which are filled with solvent that has lost its fluidity. Finally, the gel undergoes post-processing steps such as drying and sintering to prepare materials with molecular and even nanoscale substructures.

[0181] In this embodiment, the carbon source and graphite can be fully mixed by the sol-gel method, and then heat-treated to obtain a dense coating layer that is uniformly distributed on the surface of the graphite core.

[0182] In some embodiments, in order to better decompose the carbonized carbon source and form a uniformly distributed and highly dense coating layer, the heat treatment temperature is 500–1200°C and the time is 4–8 hours.

[0183] Optionally, the heat treatment temperature is 600–1000℃ and the time is 4–8 hours.

[0184] Optionally, the heat treatment temperature is independently selected from any value or a range between 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, and 1000°C.

[0185] Optionally, the heat treatment time is independently selected from any value of 4.0h, 4.5h, 5.0h, 5.5h, 6.0h, 6.5h, 7.0h, 7.5h, 8.0h, or a range between any two.

[0186] In some embodiments, the heat treatment pressure is 5 to 15 MPa.

[0187] In some embodiments, in order to better decompose the carbonized carbon source and form a uniformly distributed and highly dense coating layer, a pre-heat treatment can be performed before the heat treatment. For example, the temperature can be maintained at 80–100°C for 1–2 hours, and then at 800–1000°C for 4–6 hours.

[0188] Optionally, the heat treatment pressure is independently selected from any value or a range between 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, and 15 MPa.

[0189] Example

[0190] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0191] Example 1:

[0192] Preparation of negative electrode active materials:

[0193] 1) After IPA-Al (aluminum isopropoxide) and artificial graphite are mixed evenly by stirring, substance A1 is obtained, wherein the mass ratio of IPA-Al (aluminum isopropoxide) to artificial graphite is 1:10.

[0194] 2) Transfer substance A1 to a high-pressure reactor, maintain the temperature at 80°C for 2 hours under a pressure of 10 MPa, then raise the temperature to 900°C and maintain the temperature for 4 hours to obtain product B1.

[0195] 3) The product B1 was washed with deionized water, dried, ground and sieved to obtain graphite anode active material C1.

[0196] 4) Mix the graphite negative electrode active material C1, conductive carbon black, binder (SBR), carboxymethyl cellulose (CMC) and water in step 3) at a weight ratio of 95:1:1:3 to prepare a negative electrode slurry. Then, coat it onto copper foil, and after cold pressing and cutting, obtain a negative electrode sheet with double-sided coating material.

[0197] Example 2:

[0198] The experimental steps were basically the same as in Example 1, except that IPA-Al (aluminum isopropoxide) was replaced with IPA-Mg (magnesium isopropoxide) to obtain graphite anode active material C2 and anode sheet.

[0199] Example 3:

[0200] 1) Prepare a 10% ethanol mixed solution of IPA-Al (aluminum isopropoxide). Weigh the ethanol mixed solution and artificial graphite at a mass ratio of 1:10, stir and mix for 1 hour, and then vacuum dry at 60°C for 0.5 hours to obtain substance A3.

[0201] 2) Transfer substance A3 to a high-pressure reactor, maintain the temperature at 80°C for 2 hours under a pressure of 10 MPa, then raise the temperature to 900°C and maintain the temperature for 4 hours to obtain product B3.

[0202] 3) After washing and drying the substance B3 with deionized water, it is ground and sieved to obtain the graphite negative electrode active material C3.

[0203] 4) Mix the graphite negative electrode active material, conductive carbon black, binder (SBR), carboxymethyl cellulose (CMC), and water in step 3) at a weight ratio of 95:1:1:3 to prepare a negative electrode slurry. Then, coat the slurry onto a copper foil and, after cold pressing and cutting, obtain a negative electrode sheet with double-sided coating material.

[0204] Example 4

[0205] The experimental steps are basically the same as in Example 1, except that the heat treatment parameters in step 2) are replaced with a pressure of 15 MPa, and after holding at 80°C for 2 hours, the temperature is raised to 700°C and held for 4 hours to obtain graphite negative electrode active material C4 and negative electrode sheet.

[0206] Comparative Example 1

[0207] The experimental procedure was basically the same as in Example 1, except that IPA-Al (aluminum isopropoxide) was not added.

[0208] Comparative Example 2

[0209] The experimental steps were basically the same as in Example 1, except that IPA-Al (aluminum isopropoxide) was replaced with aluminum oxide.

[0210] 1. Separating membrane:

[0211] A polyethylene film with a thickness of 13 μm was used as the separator.

[0212] 2. Electrolyte:

[0213] Ethylene carbonate, diethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1. LiPF6 was then dissolved in this solution to obtain an electrolyte. The concentration of LiPF6 in this electrolyte was 1 mol / L.

[0214] 3. Positive electrode plate:

[0215] The positive electrode active material lithium iron phosphate, conductive carbon black, binder (polyvinylidene fluoride) and surfactant are stirred in N-methylpyrrolidone at a weight ratio of 95:1:3:1 to disperse and prepare a positive electrode slurry. The slurry is then coated on aluminum foil and cold-pressed and cut to obtain a positive electrode sheet coated with a single-sided material.

[0216] 4. Half-cell assembly:

[0217] A negative electrode half-cell was prepared using lithium sheet as the counter electrode and the negative electrode sheet used in the examples and comparative examples.

[0218] 5. Stacked three-electrode single-cell battery:

[0219] The negative electrode, the separator, the electrolyte, and the positive electrode from the examples and comparative examples were assembled into a stacked three-electrode single-cell battery in an argon-filled glove box. A double-sided anode electrode was sandwiched between two single-sided cathode electrodes, and an additional separator was added between one of the cathodes and the anode, with a copper wire placed between the two separators.

[0220] Data Analysis:

[0221] Negative electrode half-cell rate performance test: Under an ambient temperature of 25℃, the negative electrode half-cell was subjected to the first charge-discharge test, with a test voltage range of 0.05~2V; charge-discharge rate: 0.05C discharge, 0.1C charge. Then, the rate performance test was carried out, with the rates successively being 0.1C, 0.5C, 1C, 2C, 4C, 6C, and 1C, with each rate being performed for 10 cycles.

[0222] Stacked three-electrode AC impedance test: After lithium plating on copper wire using a 5uA current, the AC impedance of the stacked three-electrode battery is tested at ambient temperatures of 25℃ and -10℃. The test voltage is less than 5V and the frequency range is 500kHz-30mHz.

[0223] Stacked three-electrode charging capability test: Using a 5uA current, after lithium plating on the copper wire, the charging capability of the stacked three-electrode battery was tested at ambient temperatures of 25℃ and -10℃. Specifically, during charging at a 1C rate, the voltage between the copper wire and the negative electrode was monitored. When the voltage reached 0mV, the battery's state of charge (SOC) was calibrated. The charging capability was determined by calculating the charging time from 10% to 80% SOC.

[0224] The test results are shown in Tables 1, 2, and 3. Figures 6-7 .

[0225] Table 1: Negative Electrode Half-Cell

[0226] sample Charging capacity Discharge capacity First Coulomb efficiency Comparative Example 1 370.5 353.1 95.30％ Comparative Example 2 369.4 350.8 94.96％ Example 1 370.0 352.5 95.27％ Example 2 369.9 352.0 95.16％ Example 3 369.9 352.4 95.26％ Example 4 369.6 351.3 95.12％

[0227] Table 2: AC impedance of stacked three-electrode plates

[0228] sample Anode resistance at 25℃ / Ω Battery impedance at 25℃ / Ω -10℃ Anode resistance / Ω -10℃ Battery resistance / Ω Comparative Example 1 0.155 0.291 2.384 6.612 Example 1 0.128 0.291 1.794 6.302

[0229] Table 3: Charging Capacity of Stacked Three-Electrode Units

[0230] sample Charging time at 25℃ / min -10℃ charging time / min Comparative Example 1 33 34 Example 1 33 26

[0231] Depend on Figure 4 and Figure 5 It can be seen that a high-density coating layer was formed in the negative electrode active material of Example 1.

[0232] From Table 1-3 and Figure 6-7 It can be seen that when the negative electrode active material in Example 1 is used in a single battery cell, lower low-temperature impedance and better low-temperature charging capability can be obtained.

[0233] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A battery cell, comprising a negative electrode and a positive electrode, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material; The negative electrode active material includes a graphite core and a coating layer that covers at least part of the surface of the graphite core; The coating layer includes one or more of carbon and metallic elements; The carbon element includes amorphous carbon, and the metal element is grafted onto the surface of the graphite core and / or the coating layer via chemical bonds.

2. The battery cell according to claim 1, characterized in that, The metal element is grafted onto the surface of the graphite core and / or the coating layer via carbon-oxygen bonds.

3. The battery cell according to claim 1 or 2, characterized in that, The metal element is grafted onto the surface of the graphite core and / or the coating layer in the form of -COM groups and / or -CM groups; Wherein, M is a metallic element, including one or more of the following elements: lithium, magnesium, aluminum, titanium, calcium, zinc, and tin.

4. The battery cell according to any one of claims 1-3, characterized in that, Based on the aforementioned negative electrode active material, the mass content of the metal element is 0.1% to 10%; and / or, Based on the negative electrode active material, the graphite content is 90% to 99.9% by mass.

5. The battery cell according to any one of claims 1-4, characterized in that, The graphite includes one or more of the following: artificial graphite, natural graphite, mesophase carbon microspheres, and hard carbon.

6. The battery cell according to any one of claims 1-5, characterized in that, The average volumetric particle size Dv50 of the graphite is 1–30 μm; and / or, The average volumetric particle size Dv50 of the graphite is 5–10 μm.

7. The battery cell according to any one of claims 1-6, characterized in that, The coating layer satisfies one or more of the following conditions: The thickness of the coating layer is 1–20 nm; The compaction density of the coating layer is 1.6 g / cm³. 3 ~1.9g / cm 3 ; The coating layer covers at least 80% of the surface area of ​​the graphite core.

8. The battery cell according to any one of claims 1-7, characterized in that, The resistivity of the negative electrode active material is 1*10⁻⁶. -6 Ωm~3*10 -6 Ωm.

9. A negative electrode active material, characterized in that, The negative electrode active material includes a graphite core and a coating layer that covers at least part of the surface of the graphite core; The coating layer includes one or more of carbon and metallic elements; The carbon element includes amorphous carbon, and the metal element is grafted onto the surface of the graphite core and / or the coating layer via chemical bonds.

10. A method for preparing a negative electrode active material, characterized in that, include: A precursor is obtained by mixing a carbon source containing metal elements and graphite. The precursor is subjected to heat treatment to obtain the negative electrode active material; The negative electrode active material includes a graphite core and a coating layer that covers at least part of the surface of the graphite core; The coating layer includes one or more of carbon and metallic elements; The carbon element includes amorphous carbon, and the metal element is grafted onto the surface of the graphite core and / or the coating layer via chemical bonds.

11. The preparation method according to claim 10, characterized in that, The carbon source includes an organometallic salt, which includes one or more of metal alkoxides and metal phenolates; and / or, The graphite includes one or more of the following: artificial graphite, natural graphite, mesophase carbon microspheres, and hard carbon.

12. The preparation method according to claim 11, characterized in that, The metal alkoxide includes one or more of metal isopropoxide, metal ethanol, and metal methanol; the metal phenolic salt includes one or more of metal phenolic salt and metal nitrophenolic salt; and the metal element includes one or more of lithium, magnesium, aluminum, titanium, calcium, zinc, and tin.

13. The preparation method according to any one of claims 10-12, characterized in that, Based on the precursor, the carbon source has a mass content of 1% to 30%; Optionally, based on the precursor, the carbon source has a mass content of 5% to 20%.

14. The preparation method according to any one of claims 10-13, characterized in that, The mixing process includes one or more of the following: sol-gel method, ball milling method, and stirring method; and / or, The heat treatment is performed at a temperature of 500–1200°C for a time of 4–8 hours; and / or, The heat treatment is performed at a temperature of 600–1000℃ for a time of 4–8 hours; and / or, The heat treatment pressure is 5-15 MPa.

15. A battery device, characterized in that, Includes the battery cell according to any one of claims 1-8.

Images